a corrosion inhibitor for use as an additive to highway de-icing salt has been developed. laboratory experiments have been used as screening tests and the more promising materials have been evaluated in trials on cars. the corrosive action of salt on mild steel is almost constant over a concentration range of 10 to o.05 per cent of salt in solution. the protection given by inhibitors diminishes markedly as they become diluted and they are only effective in reducing corrosion if their initial addition is of the order of 7 per cent of salt. this has been demonstrated both in laboratory tests and in field trials. the use of this proportion of inhibitor would increase the expenditure on de-icing salt by about 25m. even though the cost of vehicle corrosion from salt exceeds this considerably, it seems unlikely that such an increase in public expenditure on salting could be justified unless almost complete protection from corrosion could be offered. a cheaper way of employing the inhibitor, as part of an automatic car washing process is being examined. (a)

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